Ablation catheter

ABSTRACT

An ablation catheter is disclosed having proximal and distal ends and an external surface, a lumen contained within the catheter body, a plurality of openings in the surface of the catheter, wherein the openings are in communication with the lumen, one or more electrodes secured within the catheter within the lumen and a source for conductive media to be introduced into the lumen to contact the electrode. The ablation catheter also may contain a conductive media flow control system which controls the flow of the conductive media through the openings in the surface of the catheter. Also disclosed is a process for ablation of human tissue which includes introducing an ablation catheter into the human body to a location to be ablated, passing a conductive media through a lumen of the catheter to contact one or more electrodes, passing the conductive media through the openings in the catheter body to contact the tissue to be ablated, and conducting energy from the electrode through the conductive media to the tissue for a sufficient period of time to ablate the tissue.

This application is a divisional application Ser. No. 09/361,811 filedon Jul. 27, 1999, now U.S. Pat. No. 6,264,654, which is a divisional ofapplication Ser. No. 08/897,300 filed Jul. 21, 1997 now U.S. Pat. No.6,080,151

FIELD OF INVENTION

This invention relates to catheters for the mapping and ablation ofhuman tissue, particularly cardiac tissue. In particular, the inventionrelates to an ablation catheter to ablate human tissue utilizingconductive media contacted by an electrode, which electrode is containedwithin the catheter.

BACKGROUND

Catheters have been in use for medical procedures for many years.Catheters can be used for medical procedures to examine, diagnose andtreat while positioned at a specific location within the body which isotherwise inaccessible without more invasive procedures. During theseprocedures a catheter is inserted into a vessel near the surface of thebody and is guided to a specific location within the body forexamination, diagnosis and treatment. For example, one procedureutilizes a catheter to convey an electrical stimulus to a selectedlocation within the human body. Another procedure utilizes a catheterwith sensing electrodes to monitor various forms of electrical activityin the human body.

Catheters are also used increasingly for medical procedures involvingthe human heart. Typically, the catheter is inserted in an artery orvein in the leg, neck or arm of the patient and threaded, sometimes withthe aid of a guidewire or introducer, through the vessels until a distaltip of the catheter reaches the desired location for the medicalprocedure in the heart.

A typical human heart includes a right ventricle, a right atrium, a leftventricle and a left atrium. The right atrium is in fluid communicationwith the superior vena cava and the inferior vena cava. Theatrioventricular septum separates the right atrium from the rightventricle. The tricuspid valve contained within the atrioventricularseptum provides communication between the right atrium and the rightventricle.

In the normal heart, contraction and relaxation of the heart muscle(myocardium) takes place in an organized fashion as electro-chemicalsignals pass sequentially through the myocardium from the sinoatrial(SA) node to the atrioventricular (AV) node and then along a welldefined route which includes the His-Purkinje system into the left andright ventricles. The AV node lies near the ostium of the coronary sinusin the interatrial septum in the right atrium. The His-Purkinje systembegins at the AV node and follows along the membranous interatrialseptum toward the tricuspid valve through the atrioventricular septumand into the membranous interventricular septum. At about the middle ofthe interventricular septum, the His-Purkinje system splits into rightand left branches which straddle the summit of the muscular part of theinterventricular septum.

Sometimes abnormal rhythms occur in the heart which are referred togenerally as arrhythmia. For example, a common arrhythmia isWolff-Parkinson-White syndrome (W-P-W). The cause of W-P-W is generallybelieved to be the existence of an anomalous conduction pathway orpathways that connect the atrial muscle tissue directly to theventricular muscle tissue, thus bypassing the normal His-Purkinjesystem. These pathways are usually located in the fibrous tissue thatconnects the atrium and the ventricle.

Other abnormal arrhythmias sometimes occur in the atria, which arereferred to as atrial arrhythmia. Three of the most common atrialarrhythmia are ectopic atrial tachycardia, atrial fibrillation andatrial flutter. Atrial fibrillation can result in significant patientdiscomfort and even death because of a number of associated problems,including: an irregular heart rate which causes patient discomfort andanxiety, loss of synchronous atrioventricular contractions whichcompromises cardiac hemodynamics resulting in varying levels ofcongestive heart failure, and stasis of blood flow, which increases thelikelihood of thromboembolism.

Efforts to alleviate these problems in the past have includedsignificant usage of pharmacological treatments. While pharmacologicaltreatments are sometimes effective, in some circumstances drug therapyhas had only limited effectiveness and is frequently plagued with sideeffects, such as dizziness, nausea, vision problems and otherdifficulties.

An increasingly common medical procedure for the treatment of certaintypes of cardiac arrhythmia is catheter ablation. During conventionalcatheter ablation procedures an energy source is placed in contact withcardiac tissue to heat the tissue and create a permanent scar or lesion.During one procedure the lesions are designed to interrupt existingconduction pathways commonly associated with arrhythmias within theheart. The particular area for ablation depends on the type ofunderlying arrhythmia. One common ablation procedure treatsatrioventricular nodal reentrant tachycardia (AVNRT). Ablation of fastor slow AV nodal pathways is disclosed in Singer, I., et al., “CatheterAblation for Arrhythmias” Clinical Manual of Electrophysiology, pgs.421-431 (1993). The use of electrode catheters for ablating specificlocations within the heart has also been disclosed, for example in U.S.Pat. Nos. 4,641,649, 5,263,493, 5,231,995, 5,228,442 and 5,281,217.

Another medical procedure using ablation catheters with sheaths toablate accessory pathways associated with W-P-W utilizing both atransseptal and retrograde approach is discussed in Saul, J. P., et al.“Catheter Ablation of Accessory Atrioventricular Pathways in YoungPatients: Use of long vascular sheaths, the transseptal approach and aretrograde left posterior parallel approach” Journal of the AmericanCollege of Cardiology, Vol. 21, no. 3, pgs. 571-583 (Mar. 1, 1993).Other catheter ablation procedures are disclosed in Swartz, J. F.“Radiofrequency Endocardial Catheter Ablation of AccessoryAtrioventricular Pathway Atrial Insertion Sites” Circulation, Vol. 87,no. 2, pgs. 487-499 (February, 1993).

Ablation of a specific location within the heart requires the preciseplacement of the ablation catheter within the heart. Precise positioningof the ablation catheter is especially difficult because of thephysiology of the heart, particularly because the heart continues tobeat throughout the ablation procedures. Commonly, the choice ofplacement of the catheter is determined by a combination ofelectrophysiological guidance and fluoroscopy (placement of the catheterin relation to known features of the heart which are marked byradiopaque diagnostic catheters which are placed in or at knownanatomical structures, such as the coronary sinus, high right atrium andthe right ventricle).

Ablation procedures using guiding introducers to guide an ablationcatheter to a particular location in the heart for treatment of atrialarrhythmia have been disclosed in U.S. Pat. Nos. 5,497,774, 5,427,119,5,575,166, 5,640,955, 5,564,440 and 5,628,316. During these procedures,ablation lesions are produced in the heart as an element of the medicalprocedure.

The energy necessary to ablate cardiac tissue and create a permanentlesion can be provided from a number of different sources. Originallydirect current was utilized although laser, microwave, ultrasound andforms of direct current (high energy, low energy and fulgutronizationprocedures) have also been utilized to perform ablation procedures.However, because of problems associated with the use of DC current,radiofrequency (RF) has become the preferred source of energy forablation procedures. The use of RF energy for ablation has beendisclosed, for example, in U.S. Pat. Nos. 4,945,912, 5,209,229,5,281,218, 5,242,441, 5,246,438, 5,281,213 and 5,293,868. The use of RFenergy with an ablation catheter contained within a transseptal sheathfor the treatment of W-P-W in the left atrium is disclosed in Swartz, J.F. et al. “Radiofrequency Endocardial Catheter Ablation of AccessoryAtrioventricular Pathway Atrial Insertion Sites” Circulation Vol. 87,pgs. 487-499 (1993). See also Tracey, C. N. “Radio Frequency CatheterAblation of Ectopic Atrial Tachycardia Using Paced Activation SequenceMapping” J. Am. Coll. Cardiol. Vol. 21, pgs. 910-917 (1993).

In addition to radiofrequency ablation catheters, thermal ablationcatheters have been disclosed. During thermal ablation procedures aheating element, secured to the distal end of a catheter, heatsthermally conductive fluid, which fluid then contacts the human tissueto raise its temperature for a sufficient period of time to ablate thetissue. A method and device for thermal ablation using heat transfer isdisclosed in U.S. Pat. No. 5,433,708. Another thermal ablation procedureutilizing a thermal electrode secured to a catheter and located within aballoon with openings in that balloon to permit heated conductive fluidintroduced into the balloon from the catheter to escape from the balloonfor contact with the tissue to be ablated is disclosed in U.S. Pat. No.5,505,730.

Conventional ablation procedures utilize a single distal electrodesecured to the tip of an ablation catheter. Increasingly, however,cardiac ablation procedures utilize multiple electrodes affixed to thecatheter body. These ablation catheters often contain a distal tipelectrode and a plurality of ring electrodes as disclosed in U.S. Pat.Nos. 5,582,609, 5,487,385, 5,228,442, 4,892,102, 5,025,786, 5,327,905,and 5,354,297.

To form linear lesions within the heart using a conventional ablationtip electrode requires the utilization of procedures such as a “dragburn”. During this procedure, while ablating energy is supplied to thetip electrode, the tip electrode is drawn across the tissue to beablated, producing a line of ablation. Alternatively, a series of pointsof ablation are formed in a line created by moving the tip electrodeincremental distances across the cardiac tissue. The effectiveness ofthese procedures depends on a number of variables including the positionand contact pressure of the tip electrode of the ablation catheteragainst the cardiac tissue, the time that the tip electrode of theablation catheter is placed against the tissue, the amount of coagulumthat is generated as a result of heat generated during the ablationprocedure and other variables associated with a beating heart,especially an erratically beating heart. Unless an uninterrupted trackof cardiac tissue is ablated, unablated tissue or incompletely ablatedtissue may remain electrically active, permitting the continuation ofthe reentry circuit which causes the arrhythmia.

It has been discovered that more efficient ablation may be achieved if alinear lesion of cardiac tissue is formed during a single ablationprocedure. The production of linear lesions in the heart by use of anablation catheter is disclosed in U.S. Pat. Nos. 5,487,385, 5,582,609and Ser. No. 08/407,448. A specific series of linear lesions formed inthe atria for the treatment of atrial arrhythmia are disclosed in U.S.Pat. No. 5,575,766.

The ablation catheters commonly used to perform these ablationprocedures produce scar tissue at a selected location by physicalcontact of the cardiac tissue with an electrode of the ablationcatheter. Conventional tip electrodes with adjacent ring electrodescannot perform this type of procedure, however, because of the highamount of energy that is necessary to ablate sufficient tissue toproduce a complete linear lesion. Also, conventional ring electrodes mayleave holes or gaps in the linear ablation lesion when used to ablatecardiac tissue, which can provide a doorway through the lesion for thecreation of a new reentry circuit.

An ablation catheter for use in the heart which contains a pair ofintertwined helical electrodes is disclosed in U.S. Pat. No. 5,334,193.The helically wound electrode is affixed to the surface of the catheterbody over a distance of about 8 cm. from the distal tip of the catheterbody. Other helical electrodes are disclosed in U.S. Pat. Nos.5,542,928, 4,776,334, 5,047,026, 4,934,049, 4,860,769, and 4,161,952 andWO 95/10319.

During conventional ablation procedures, the ablating energy isdelivered directly to the cardiac tissue by an electrode on the catheterplaced against the surface of the tissue to raise the temperature of thetissue to be ablated. This rise in tissue temperature also causes a risein the temperature of blood surrounding the electrode, which oftenresults in the formation of coagulum on the electrode, which reduces theefficiency of the ablation electrode.

To achieve efficient and effective ablation, coagulation of blood thatis common with conventional ablation catheters should be avoided. Thiscoagulation problem can be especially significant when linear ablationlesions or tracks are produced because such linear ablation proceduresconventionally take more time than ablation procedures ablating only asingle location.

It is accordingly an aspect of the invention to disclose a catheter forablating tissue within the human heart.

It is a still further aspect of the invention to disclose a cathetercontaining one or more electrodes located within a lumen in the catheterbody useful for creating linear ablation lesions.

It is a still further aspect of the invention to disclose an ablationcatheter containing one or more electrodes located within a lumen in thecatheter and a plurality of openings in the surface of the catheter bodyin communication with the electrode.

It is a still further aspect of the invention to disclose an ablationcatheter containing one or more electrodes located within a lumen in thecatheter, a plurality of openings in the surface of the catheter incommunication with the electrodes and a structure for the introductionof a conductive media through the lumen to contact the electrodes andthen be expelled from openings in the catheter body.

It is a still further aspect of the invention to disclose an ablationcatheter useful for formation of a linear ablation lesion within theheart utilizing a catheter body containing one or more electrodeslocated within a lumen in the catheter body, conductive media passingthrough the lumen conductively in contact with the electrodes, andopenings in the catheter body through which the conductive media passesto contact cardiac tissue for ablation.

It is a still further aspect of the invention to disclose an ablationcatheter containing a catheter body with one or more coiled electrodeslocated within a lumen, a plurality of openings in the surface of thecatheter body in communication with the coiled electrodes and the lumen,a conductive media passing through the lumen substantially in contactwith the coiled electrodes and a structure in the catheter body whichcontrols the flow of the conductive media through the openings in thesurface of the catheter body.

It is a still further aspect of the invention to disclose an ablationcatheter for use in the formation of a linear ablation lesion within theheart utilizing a catheter body containing one or more electrodeslocated within a lumen in the catheter body, conductive media passingthrough the lumen substantially in contact with the electrodes, openingsin the catheter body through which the conductive media passes tocontact cardiac tissue for ablation and a structure for guiding thecatheter to the location to be ablated.

It is a still further aspect of the invention to disclose an ablationcatheter for use in the formation of a linear ablation lesion within theheart utilizing a catheter body containing one or more electrodeslocated within a lumen in the catheter body, conductive media passingthrough the lumen, wherein the conductive media is substantially incontact with the electrodes, openings in the catheter body through whichthe conductive media passes to contact the cardiac tissue to be ablatedand a rail for guiding the ablation catheter to the location to beablated.

It is a still further aspect of the invention to disclose an ablationcatheter for use in the formation of a linear ablation lesion within theheart utilizing a catheter body containing one or more electrodeslocated within a lumen in the catheter body, conductive media passingthrough the lumen wherein the conductive media is substantially incontact with the electrodes, openings in the catheter body through whichthe conductive media passes to ablate the cardiac tissue and a guidewirefor guiding the ablation catheter to the location to be ablated.

It is a still further aspect of the invention to disclose a method forablation of cardiac tissue by use of an ablation catheter containing oneor more electrodes within a lumen in a catheter body by passingconductive media through the lumen where the conductive media issubstantially in contact with the electrode and expelling the conductivemedia through the openings in the catheter body to contact the cardiactissue for ablation.

These and other aspects of the invention can be provided by the catheterfor the mapping and ablation of cardiac tissue which is disclosed by thepresent invention.

SUMMARY OF INVENTION

The present invention relates to an ablation catheter for ablation ofhuman tissue. The catheter includes a catheter body with proximal anddistal ends containing one or more lumen extending through the catheterbody from its proximal to, or near, its distal end. A plurality ofopenings is provided in the surface of the catheter in communicationwith one of the lumens. One or more electrodes are secured within thelumen inside the catheter body. A system for introduction of aconductive media into the lumen is provided such that the media isconductively in contact with the electrodes. The invention also includesa system to control the flow of the conductive media through the lumenand out through the openings in the surface of the catheter.

Preferably, the openings are extended in a linear line down the side ofthe catheter.

Preferably, the electrodes constitute one or more coiled electrodesextending down the length of the lumen inside the catheter body.

Preferably the energy source conducted by the conductive media isradiofrequency energy.

Also disclosed is a process for the ablation of human tissue,particularly for the production of a linear lesion in the heart. Duringthe procedure an ablation catheter is introduced into the heart to alocation to be ablated. The ablation catheter includes a catheter body,a lumen passing through the catheter body, a plurality of openings inthe surface of the catheter in communication with the lumen, and one ormore electrodes secured within the lumen of the catheter body. Aconductive media is passed through the lumen of the catheter where itconductively contacts the electrode contained within the lumen. The flowof the conductive media through the lumen is controlled so that themedia is expelled through the openings in the catheter body such thatthe conductive media contacts the tissue to be ablated. Energy, such asradiofrequency energy, is conducted from the electrode by the conductivemedia to the tissue to be ablated for a sufficient period of time toablate the tissue.

Preferably the energy conducted by the conductive media forms a linearlesion in the tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the ablation catheter of the present invention.

FIG. 2 is a cross section, side view of a distal portion of the ablationcatheter placed against tissue to be ablated.

FIG. 3 is an enlarged, side cross section view of the distal portion ofthe ablation catheter as shown in FIG. 2.

FIG. 4 is a cross section view of the ablation catheter taken along theline 4—4 in FIG. 3.

FIG. 5 is a cross section view of the ablation catheter taken along theline 5—5 in FIG. 3.

FIG. 6 is a side view of a distal portion of the ablation cathetershowing a line of openings extending along a portion of the catheterbody.

FIG. 7 is a side view of an alternative embodiment of the distal portionof the ablation catheter showing two lines of openings extending along aportion of the catheter body.

FIG. 8 is a cross section view of the distal portion of the ablationcatheter showing an alternative embodiment of the present inventionwherein the gap between individual coils of the electrode containedwithin the lumen varies from the proximal to the distal end of theelectrode.

FIG. 9 is a cross section view of the distal portion of the ablationcatheter in an alternative embodiment where the diameter of theelectrode contained within the lumen increases from the proximal to thedistal end of the electrode.

FIG. 10 is a cross section view of the distal portion of the ablationcatheter in a further alternative embodiment where the electrodecontained within the lumen includes a conductively coated tubularelement containing a series of openings.

FIG. 11 is a cross section view of the distal portion of the ablationcatheter showing a further alternative embodiment where the electrodecontained within the lumen includes a filter element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The ablation catheter (10) of the present invention as shown in FIGS. 1,2 and 3 is comprised of a catheter body (12) with a proximal end (14)and a distal end (16), at least one lumen (18) extending lengthwisesubstantially through the catheter body (12), a plurality of openings(20) in the surface of the catheter body (12) extending through theoutside surface (21) of the catheter body (12) into the lumen (18), anelectrode (22), or plurality of electrodes, secured within the lumen(18), and a system for introduction of a conductive media into the lumen(18), whereby the conductive media contacts the electrode (22) orelectrodes as the media passes through the lumen (18) and is expelledout the openings (20) in the catheter body (12) to contact tissue (23)to be ablated. There is also preferably provided a system to control theflow of the conductive media through the lumen (18) to create areasonably consistent flow of conductive media out through substantiallyall of the openings (20) in the surface of the catheter body (12).

The catheter body (12) is a conventional elongated catheter made ofmaterials suitable for use in humans, such as nonconductive polymers.Exemplary polymers used for the production of the catheter body includethose well known in the art such as polyurethanes, polyether-blockamides, polyolefins, nylons, polytetrafluoroethylene, polyvinylidenefluoride, and fluorinated ethylene propylene polymers and otherconventional materials.

The length of the catheter (10) is preferably from about 50 cm to about150 cm (20 to 60 in.). The diameter of the catheter (10) is withinranges well known in the industry, preferably, from about 4 to 16 Frenchand more preferably from about 6 to 8 French (1 French equals ⅓ of amillimeter (0.013 in.)).

The catheter body (12) preferably contains one or more lumens extendingthrough the catheter body (12) from its proximal end to near its distalend as shown in FIGS. 4 and 5.

Preferably, sufficient lumens are present in the catheter body (12) toaccommodate wires for one or more sensing electrodes, preferably asingle tip electrode (30), thermosensing devices, such as thermocouples(32), and the electrode (22) or electrodes used to contact theconductive media as shown in FIG. 3, as well as to accommodate the flowof the conductive media. In addition, in a preferred embodiment, one ofthe lumens also contains a system to control the movement of theablation catheter. In one embodiment this system is a pull wire (24).

The lumen (18) of the catheter (10) in which the electrode (22) orelectrodes are secured is in communication with the openings (20) andextends from the proximal end (14) of the catheter to near its distalend (16). The diameter of the lumen (18) should be sufficient toaccommodate the electrode (22) or electrodes passing through the lumen,as well as to permit the flow of conductive media through the lumen (18)during the ablation procedure. Preferably, the lumen (18) should have adiameter of at least about 0.2 mm (0.008 in.) and preferably from about0.3 mm (0.01 in.) to about 1.0 mm (0.04 in.).

There are preferably a plurality of openings (20) in the surface (21) ofthe distal portion (16) of the catheter (10), each of which are incommunication with the lumen (18). Preferably, these openings (20) areformed into a linear line along the length of the catheter as shown inFIG. 6. The openings (20) can be of any size or shape that permit thepassage of the conductive media through the lumen of the catheterwithout compromising the structural integrity of the catheter. Thenumber of individual openings (20) of the catheter is from about 2 toabout 100 individual openings, preferably 3 or more.

Preferably the openings (20) are circular in cross section with adiameter of about 0.25 mm (0.01 in) to about 2.5 mm (0.1 in). Thedistance between the openings (20) should be restricted such thatsufficient conductive media is expelled through adjacent openings (20)to contact the tissue to be ablated and conduct sufficientradiofrequency energy to the tissue to form an adequate linear ablationlesion. In a preferred embodiment, the distance between the individualopenings (20) does not exceed about 4.0 mm (0.16 in.) and preferablydoes not exceed from about 0.5 mm (0.02 in.) to about 1.5 mm (0.06 in.).The openings (20) extend substantially along the length of the catheterbody (12) at least about 0.5 cm. (0.2 in.), preferably as much as about6.0 cm. (2.4 in.).

In an alternative preferred embodiment, the openings (20) in thecatheter body (12) are formed in a pair of linear lines approximatelyparallel to each other extending along the length of the catheter body(12) as shown in FIG. 7. By using a pair of linear lines, it is possibleto form a wider ablation lesion. In a preferred embodiment, openings(20) are provided in the catheter body (12) through to the lumen (18) ator close to both the proximal end (27) and distal end (25) of thatportion of the lumen which contains, or may contain, an electrode, asshown in FIG. 3. By this structure, the possibility of pooling ofconductive media in the lumen is reduced. Such pooling could lead to hotspots within the lumen which may reduce the effectiveness of theablation catheter. A portion of the electrode wire (34) which, may ormay not be coated, connects to the electrode (22) and may be presentwithin the lumen (18) at the point where the electrode wire is connectedto the coils (26) of the electrode (22).

The electrode wire (34), which is secured to the electrode (22) orelectrodes, passes through the catheter body (12) through a lumen (29)outside of the lumen (18) which contains the electrode (22) and entersthe lumen (18) where it is secured to the electrode (22) or electrodes,preferably at the distal end of the electrode (22) by an adhesive seal(28) as shown in FIG. 3. The electrode (22) or electrodes extend throughthe lumen (18) at least about 4 mm. (0.15 in.) and preferably from about1 cm. (0.4 in.) to about 6 cm. (2.4 in.). The electrode (22) canconstitute a single electrode or multiple electrodes, preferably 2 to 5electrodes, each of which are secured to separate electrode wires. Forpurposes of this discussion however, the electrode utilized is a singleelectrode, recognizing that multiple electrodes are an alternativeembodiment.

In one preferred embodiment, the electrode (22) is in the form of acoiled electrode containing a series of individual coils (or turns) (26)as shown in FIG. 3. The coiled electrode (22) is formed fromconventional electrode wire material, such as platinum or nickel, wherethe diameter of the wire which forms each of the coils (26) of theelectrode (22) is preferably from about 0.02 mm (0.001 in) to about 0.4mm (0.015 in). The individual coils (26) of the coiled electrode (22)are spaced sufficiently close to each other to contact the conductivemedia and thus conduct the energy, preferably radiofrequency energy,through the conductive media as it passes through the lumen (18) andover and around the coils (26) without unduly restricting the flow ofthe conductive media through the openings (20) in the catheter body(12). The flow around the coils should be sufficient to cool theelectrode (22) or electrodes during the ablation procedure, whichreduces the likelihood of formation of coagulum. Preferably, the flow ofconductive media is maintained at a positive pressure throughout theablation procedure to prevent any substantial flow of blood into theinside of the catheter body (12) where that blood might contact theelectrode (22) or electrodes. The flow of conductive media is maintainedby a conventional fluid flow pump (not shown) with a conventional stopcock and tubing (36).

By retaining the electrode (22) within the lumen (18) of the catheter(10) and by forcing the conductive media out the openings (20) in thecatheter body (12) under a positive pressure, the electrode (22) doesnot directly contact the tissue or blood present in the chamber wherethe ablation procedure is performed. This reduces both coagulum buildupand the likelihood of clot formation. In addition, the electrode (22) isconstantly being cooled by the passage of the conductive media throughthe lumen (18).

The electrode (22) contacts the conductive media as it passes throughthe lumen (18) of the catheter body (12). After such contact by theelectrode, the conductive media passes through the openings (20) in thecatheter body (12) to contact the cardiac tissue adjacent to theopenings (20). The flow of the conductive media through these openingsshould be positive, preferably at least about 1 ml. per minute and morepreferably about 10 ml. per minute. In a preferred embodiment, theconductive media is a conventional saline solution or other conductivemedia as are well known in the industry.

The preferred source for energy emitted by the electrode (22) isradiofrequency energy, although other sources for energy can be utilizedincluding direct current, laser, ultrasound and microwave. During theablation procedure the radiofrequency energy from the electrode isconducted by the conductive media to the tissue to be ablated. In onepreferred embodiment, the impedance of the conductive media is less thanthat of the impedance of the human tissue so that the human tissue willheat to an ablation temperature at a faster rate than does theconductive media. If sufficient energy is conducted to the tissue for asufficient period of time, a satisfactory ablation lesion is formed. Thelesion being formed should have an adequate depth along the entirelength of the lesion to avoid gaps that have been present with certainprior art ablation procedures.

The gap between individual coils of the coiled electrode may vary fromno separation to a range of about 0.025 mm (0.001 in.) to about 0.5 mm.(0.02 in.). In addition, the gap (104) between the individual coils(106) may vary down the length of the electrode (108), as shown in FIG.8.

The outside diameter of the electrode may also vary down the length ofthe electrode as shown in FIG. 9. The largest outside diameter (203) ofthe coiled electrode (204) is approximately equivalent to the diameterof the lumen (205) containing that electrode. The shape or angle of thecoils along the length of the lumen is not particularly important and isgenerally a function of the pitch of the individual coils. Adjustmentsto the shape of the coils within the lumen which may affect the flow ofthe conductive media through the lumen are within the contemplation ofthis invention.

In order to form a consistent ablation lesion, it is important that theconductive media passing through the openings of the catheter body isexpelled through substantially all of the openings. Any structuralsystem which accomplishes this goal of controlling the flow of theconductive media through these openings is within the scope of thisinvention.

In one preferred embodiment of the ablation catheter (100) as shown inFIG. 8, control of the flow of the conductive fluid through the openings(102) in the ablation catheter (100) is accomplished by varying the gap(104) between individual, adjacent coils (106) of the electrode (108)along the length of the lumen (110). In this preferred embodiment, thegap (104) between individual adjacent coils (106) of the electrode (108)incrementally increases from virtually no space between the coils (106)at the proximal end (112) of the electrode (108), to a distance of about0.0025 mm (0.0001 in.) to about 0.5 mm (0.02 in.) at the distal end(114) of the electrode (108).

When this structural system is utilized to control the flow of theconductive media, the conductive media is introduced into the proximalend (112) of the lumen (110) containing the electrode (108). Flow isinside the coils (106) of the electrode (106). More pressure is createdon the flow of the conductive media by this structure at the proximalend (112) of the electrode (108) than at a location more distal becausethere is an increasing gap (104) between individual coils (106) alongthe length of the catheter (100) from proximal end (112) to distal end(114). This control of the flow of the conductive media through theinside of the coiled electrode (108) results in a reasonably consistentflow of the conductive media through and around the coils (106) of theelectrode down the length of the catheter (100). By regulating the flowthrough the individual coils (106) of the electrode (108), a reasonablyconsistent flow of conductive media is also provided through theopenings (102) in the surface of the catheter (100), as shown by arrows115.

In a further alternative embodiment of the ablation catheter (200) or asan additional element of the previously discussed embodiment, the flowof the conductive fluid through the openings (202) of the catheter (200)can be controlled by varying incrementally the inner diameter of theinside space within the coils of the electrode (204) over its length, asshown in FIG. 9. When the inner diameter of the space inside the coiledelectrode (204) increases, the resistance to flow of the conductivemedia through the electrode (204) decreases. In this embodiment, theinner diameter of the electrode (204) increases from about 0.05 mm(0.002 in) to about 2.5 mm (0.1 in) near the proximal end (206) of theelectrode until it reaches its maximum outside diameter at its distalend (208), which is approximately equivalent to the diameter of thelumen (210), preferably about 0.2 mm (0.008 in) to about 2.5 mm (0.1in).

To secure the electrode (204) within the lumen (210), the proximal end(206) of the electrode (200), or the most proximal end of the firstelectrode, if more than one electrode is used, is sealed in place withinthe lumen (210), preferably with an adhesive material (212). Thisadhesive material (212) also blocks the flow of the conductive mediaaround the outside of the electrode (204) and forces the conductivemedia to flow inside the coils of the electrode (204) then flows out thegaps in the coil and out the openings (202) in the catheter (200), wherethe conductive media contacts the cardiac tissue to be ablated.

In another preferred embodiment which is a combination of theembodiments shown in FIGS. 8 and 9, the structure and shape of theelectrode is modified by varying both the gap between the individualcoils of the electrode over the length of the electrode and the innerdiameter of individual coils of the electrode over the length of theelectrode. By varying the structure of the electrode in this manner, theflow of the conductive media out of the openings can be controlled sothat it is relatively consistent through substantially all of theopenings in the catheter body.

In a further preferred alternative embodiment of the ablation catheter(300) shown in FIG. 10, the electrode (302) of the catheter (300)includes a tubular body (304) coated with an electrically conductivecoating and containing a series of openings (306) of varying sizesand/or spacing over the length of the tubular body (304). The tubularbody (304) is produced from conventional flexible conductively coatablematerials, such as polyurethanes, polyether-block amides, polyolefins,silicone, nylons, polytetrafluoroethylene, polyvinylidene fluoride, andfluorinated ethylene propylene polymers and other conventionalmaterials. The conductive coating is applied by conventional methods,such as spraying, printing or vacuum deposition. In order to render thetubular body (304) electrically conductive, it is connected to aconventional electrode wire (308) by conventional procedures.

The size of the openings (306) in the tubular body (304) vary,preferably increasing incrementally over the length of the catheter(300). Preferably, the openings (306) vary from about 0.01 mm (0.0004in) to about 1.0 mm (0.04 in). If the inside diameter of the tubularbody (304) remains constant and the openings (306) in the tubular body(304) increase in size and/or spacing incrementally over the length ofthe tubular body (304), the rate of flow of the conductive media out ofthe openings (310) in the catheter body is generally consistent.

In one embodiment of the alternative embodiment, the tubular body (304)has an outside diameter approximately equal to the diameter of the lumen(312) of the catheter (300). Alternatively, the tubular body (304) mayhave an outside diameter slightly less than the diameter of the lumen(312) of the catheter which will permit the conductive fluid to passthrough the openings (306) in the tubular body (304) to substantiallyaround the tubular body and substantially fill the space within thelumen. The length of the tubular body (304) is preferably approximatelythe same length as that portion of the catheter (300) that containsopenings (310) in the catheter body.

Referring to FIG. 11, a further alternative embodiment of the ablationcatheter (400) is shown. The electrode (402) of the catheter (400)includes a tubular, porous conductive filter element (404) connected toa source of energy, preferably radiofrequency energy, such as a wireelectrode (408). The conductive media passes through the tubular, porousconductive filter element (404) and is conductively contacted by theelectrode. The conductive media then passes out the openings (410) inthe catheter body (412). The diameter of the filter element (404) isapproximately the same as the diameter of the lumen (406) of thecatheter (400). The filter element (404) is constructed of material witha decreasing density from proximal end (414) to distal end (416) of thefilter element (404) SO that the conductive media passes through thefilter element (404) at a varying rate over the length of the filterelement (404). The density of this filter element (404) over its lengthis adjusted by conventional means to equalize substantially the flow ofthe conductive media through the filter element (404).

Any system for contacting the conductive media with energy can beutilized with this conductive filter element. In one preferredembodiment a wire electrode (408) is passed through or around theconductive filter element (404). Alternatively, a conductive coating maybe placed on or through the conductive filter element (404) which itselfis attached to a wire electrode.

In a preferred embodiment, filter element (404) is produced from amaterial which controls the flow of the conductive media such assintered metal, woven wire, felted stainless steel fiber or conductivelycoated engineered porous polymer materials, preferably a polypropylenemicrofiber.

Other embodiments of this invention which result in a method and devicewhich controls the flow of the conductive media out the openings in thecatheter body are also within the scope of this invention.

The ablation catheter may be guided to and held in the positionnecessary for the ablation procedure by conventional medical devicessuch as introducers. Alternatively, or in addition to the use of anintroducer, and in a preferred embodiment, a system is utilized toassist the ablation catheter to move to the location for the ablationprocedure. In one preferred embodiment as shown in FIG. 3, a pull wire(24) is secured into the catheter (10) through a lumen to be used tosteer the ablation catheter (10). The structure and composition of thepull wire is conventional.

Alternatively, a guidewire (not shown) can be used to assist in theplacement of the ablation catheter in the position necessary for theablation procedure.

In another alternative embodiment, the structure of the ablationcatheter can be modified to allow the ablation catheter to pass over arail (not shown) which is introduced into the location for the ablationprocedure.

Preferably, temperature sensors, such as thermistors or thermocouples(32) as shown in FIG. 3, are secured to the surface of the catheter tomonitor the temperature of the tissue being ablated.

In addition to the electrode (22) used to contact the conductive media,a sensing electrode or electrodes to monitor electrical activity may besecured to the catheter, such as a tip electrode (30) secured at or nearthe distal tip of the catheter (10) as shown in FIG. 3. Preferably thetip electrode (30) is secured to an electrode wire passing through thecatheter body (12) of the ablation catheter (10).

In operation, a modified Seldinger technique is normally used for theinsertion of the associated dilators, introducers and ablation catheterinto the body. The appropriate vessel is accessed by needle puncture.The soft flexible tip of an appropriately sized guidewire is theninserted through, and a short distance beyond, the needle into thevessel. Firmly holding the guidewire in place, the needle is removed.The guidewire is then advanced through the vessel into the appropriateportion of the heart for the ablation procedure. A preformed, shapedguiding introducer or guiding introducer system, such as those disclosedin U.S. Pat. No. 5,575,766, may be utilized to assist in properplacement of the ablation catheter (10) in the heart. Alternatively, oradditionally, the ablation catheter (10) may contain a mechanism to makeit steerable, such as a pull wire (24) as shown in FIG. 3, so that theablation catheter (10) may be guided within the vessel or chamber of thehuman body to be ablated without use of a guiding introducer. Theablation catheter can also be directed to the location to be ablated byother steering mechanism, such as a rail or a guidewire.

In one embodiment, with a guidewire in place, the dilator is placed overthe guidewire with the appropriate guiding introducer, or guidingintroducer system. The dilator and the guiding introducer or guidingintroducer system generally form an assembly to be advanced togetheralong the guidewire into the appropriate vessel. After insertion of theassembly, the guidewire is then withdrawn.

The guiding introducer or guiding introducer system for use in the heartis then passed over the guidewire through its lumen and positioned toallow ablation and mapping procedures to be performed at the appropriatelocation in the heart. Once the guiding introducer or guiding introducersystem is in place at the appropriate location within the heart, theablation catheter (10) is advanced through the lumen of the guidingintroducer or guiding introducer system.

After the desired location for ablation is determined, and the ablationcatheter has been guided to that location, the portion of the catheterbody (12) containing openings (20) is placed at or near the tissue (23)to be ablated as shown in FIG. 2. Placement of the portion of thecatheter body containing the openings (20) against the tissue to beablated is achieved by conventional procedures such as fluoroscopy, theuse of markers or other conventional methods. A conductive media is thenpassed through the lumen (18) of the ablation catheter (10), where itpasses around the electrode (22).

Several different embodiments exist for the structure of the electrode(22). In one preferred embodiment the electrode (22) is a coiledelectrode, or a series of interconnected coiled electrodes, which mayhave the same or a different gap between the individual coils of theelectrode, so that the flow of the conductive media through the openings(20) in the catheter body (12) is generally consistent over the lengthof the catheter body (12). Other alternative embodiments for theelectrode (22) as discussed in the application can be utilized as longas the flow of the conductive media through the openings (20) over thelength of the catheter body (12) is generally consistent.

After contact with the electrode, the conductive media then passes outthrough the openings (20) in the ablation catheter (10) where itcontacts the tissue to be ablated. The conductive media conducts theenergy, preferably radiofrequency energy, generated by the electrode(22) to the surface of the tissue to be ablated. The conductive mediacontinues to pass through the openings (20) to contact the tissue for asufficient period of time to permit the radiofrequency energy to formthe ablation lesion or tract.

Thermosensing devices, such as thermocouples (32), are secured to theablation catheter (10) to determine whether sufficient energy has beenapplied to the tissue to create an adequate linear lesion. After theablation procedure is completed, a sensing electrode, such as a tipelectrode (30), may be utilized as a sensing system to determine if thearrhythmia has been eliminated at the particular location within theheart. Additional ablation lesions or tracks can then be produced usingthe ablation catheter (10) at the same or different locations within theheart.

The device of the instant invention is designed to produce a linearlesion without exposing the surface of the ablation electrode to directcontact either with blood or cardiac tissue. In addition, the processdisclosed herein provides an efficient procedure for the creation oflinear lesions and ablation tracks without the associated problemspresent with prior art devices.

By retaining the electrode within the lumen of the catheter and byforcing the conductive media out the openings in the catheter body, theelectrode does not directly contact the cardiac tissue or the bloodpresent in the chamber where the ablation procedure is performed. Thisreduces both coagulum buildup and the likelihood of clot formation.

Pharmacological treatments may also be used in combination with ablationprocedures to relieve the atrial arrhythmia.

It will be apparent from the foregoing that while particular forms ofthe invention have been illustrated and described, various modificationscan be made without departing from the spirit and scope of theinvention.

I claim:
 1. An ablation catheter comprising (a) a catheter body withproximal and distal ends and an external surface, (b) a lumen within thecatheter body, (c) a plurality of conductive media outlet openings inthe external surface of the catheter body which are in communicationwith the lumen, wherein the conductive media outlet openings comprise alinear line of openings extended down the catheter body, (d) anelectrode fixedly secured to the catheter body and located within thelumen, (e) an introduction system to introduce a conductive media intothe lumen to contact the electrode, and (f) a conductive media flowcontrol system structured to expel the conductive media through theconductive media outlet openings, wherein the conductive media flowcontrol system is capable of regulating the flow of conductive mediathrough the conductive media outlet openings to form a reasonablyconsistent flow of the conductive media through substantially all of theconductive media outlet openings.
 2. The ablation catheter of claim 1wherein the electrode comprises a plurality of individual electrodes. 3.The ablation catheter of claim 1 whereas the electrode comprises acoiled electrode.
 4. The ablation catheter of claim 1 wherein theconductive media is a saline solution.
 5. The ablation catheter of claim1 further comprising a steering system to adjust the position of thecatheter.
 6. The ablation catheter of claim 5 wherein the steeringsystem comprises a pull wire.
 7. The ablation catheter of claim 1wherein the introduction system comprises a fluid flow pump.
 8. Theablation catheter of claim 1 further comprising a tip electrode.
 9. Anablation catheter comprising (a) a catheter body with proximal anddistal ends and an external surface, (b) a lumen within the catheterbody, (c) a plurality of conductive media outlet openings in theexternal surface of the catheter body which are in communication withthe lumen, wherein the conductive media outlet openings comprise alinear line of openings extended down the catheter body, (d) anelectrode fixedly secured to the catheter body and located within thelumen, (e) an introduction system to introduce a conductive media intothe lumen to contact the electrode, and (f) a conductive media flowcontrol system structured to expel the conductive media through theconductive media outlet openings, wherein the conductive media flowcontrol system is substantially contained within the lumen of thecatheter body, and wherein the conductive media flow control system iscapable of regulating the flow of conductive media through theconductive media outlet openings to form a reasonably consistent flow ofthe conductive media through substantially all of the conductive mediaoutlet openings.
 10. The ablation catheter of claim 9 wherein theelectrode comprises a plurality of individual electrodes.
 11. Theablation catheter of claim 9 whereas the electrode comprises a coiledelectrode.
 12. The ablation catheter of claim 9 wherein the conductivemedia is a saline solution.
 13. The ablation catheter of claim 9 furthercomprising a steering system to adjust the position the catheter. 14.The ablation catheter of claim 13 wherein the steering system comprisesa pull wire.
 15. The ablation catheter of claim 9 wherein theintroduction system comprises a fluid flow pump.
 16. The ablationcatheter of claim 9 further comprising a tip electrode.
 17. A processfor catheter ablation of human tissue comprising (a) introducing anablation catheter into a location within the human body to be ablated,wherein the ablation catheter comprises a catheter body, a lumen withinthe catheter body, a plurality of conductive media outlet openings in anexternal surface of the catheter body which are in communication withthe lumen, wherein the conductive media outlet openings comprise alinear line of openings extending down the catheter body, an electrodefixedly secured to the catheter body located within the lumen, anintroduction system capable of introducing a conductive media into thelumen, and a conductive media flow control system structured to expelthe conductive media through substantially all of the conductive mediaoutlet openings, wherein the conductive media flow control system iscapable of regulating the flow of conductive media through theconductive media outlet openings to form a reasonably consistent flow ofthe conductive media through substantially all of the conductive mediaoutlet openings, (b) passing conductive media through the lumen of thecatheter body to contact the electrode, (c) expelling the conductivemedia through substantially all of the conductive media outlet openingsin the catheter body in a reasonably consistent flow to contact thehuman tissue, and (d) conducting energy from the electrode to the humantissue using the conductive media for a sufficient period of time toablate the tissue.
 18. The process of claim 17 further comprisingforming a linear lesion in the human tissue.
 19. A process for catheterablation of human tissue comprising (a) introducing an ablation catheterinto a location within the human body to be ablated, wherein theablation catheter comprises a catheter body, a lumen within saidcatheter body, a plurality of conductive media outlet openings in anexternal surface of the catheter body which are in communication withthe lumen, wherein the conductive media outlet openings comprise alinear line of openings extending down the catheter body and anelectrode fixedly secured to the catheter body located within the lumen,an introduction system capable of introducing a conductive media intothe lumen, and a conductive media flow control system structured toexpel the conductive media through substantially all of the conductivemedia outlet openings, and wherein the conductive media flow controlsystem is contained substantially within the lumen of the catheter body,and wherein the conductive media flow control system is capable ofregulating the flow of conductive media through the conductive mediaoutlet openings to form a reasonably consistent flow of the conductivemedia through substantially all of the conductive media outlet openings,(b) passing a conductive media through the lumen of the catheter body tocontact the electrode, (c) expelling the conductive media throughsubstantially all of the conductive media outlet openings in thecatheter body in a reasonably consistent flow to contact the humantissue, and (d) conducting energy from the electrode to the human tissueusing the conductive media for a sufficient period of time to ablate thetissue.
 20. The process of claim 19 further comprising forming a linearlesion in the human tissue.